Factorial

Problem

Given a positive integer, N. Find the factorial of N.

Examples:

Example 1:

Input:
N = 5
Output:
120
Explanation:
5*4*3*2*1 = 120

Example 2:

Input:
N = 4
Output:
24
Explanation:
4*3*2*1 = 24

Your task:

You don't need to read input or print anything. Your task is to complete the function factorial() which takes an integer N as input parameters and returns an integer, the factorial of N.

• Expected Time Complexity: $O(N)$
• Expected Auxiliary Space: $O(1)$

Constraints:

• $0 <= N <= 18$

Solution

Python

def factorial (self, N):
    fact = 1
    for i in range(1, N+1):
        fact = fact*i
    return fact

Java

static long factorial(int N){
    long fact = 1;
    for (int i = 1; i<=N; i++)
        fact = fact*i;
    return fact;
}

C++

long long int factorial(int N){
    long fact = 1;
    for (int i = 1; i<=N; i++)
        fact = fact*i;
    return fact;
}

C

long long int factorial(int N){
   long fact = 1;
    for (int i = 1; i<=N; i++)
        fact = fact*i;
    return fact;
}

• Time Complexity: $O(N)$
• Auxiliary Space: $O(1)$